Photo: RenineR (Shutterstock)
If you have a snowblower, lawnmower, or other gasoline-powered device, chances are you also have a can of gas sitting around to power it. But if you bought that gas in the winter and plan to use it in the summer, or vice versa, you may find that your mower or blower doesn’t work as well as it should. Why not? Blame the gas.
Winter gasoline has a higher RVP
You already know how water responds to heat and cold, right? If you set out a dish of water on your driveway in summertime, it will evaporate pretty quickly. Do the same on a chilly day, and it will evaporate slowly if at all.
Gasoline is also affected by temperature. On a cold day, gasoline still needs to be volatile enough to turn into vapor as you start your engine. Winter gasoline is formulated to have a higher Reid vapor pressure (RVP), so it can still evaporate enough to do its job even when it’s freezing out.
For these reasons, you’ll want to use winter gasoline in your snowblower or generator in the winter. If you’ve saved summer gasoline to use in the winter, you may have trouble starting your devices, and the engine might misfire.
Summer gasoline is more fuel-efficient
Summer gasoline is the opposite: It’s formulated with a lower RVP because in the heat it could evaporate too much. This can cause problems with your engine, and can also contribute to emissions.
The EPA sets an RVP limit for gasoline sold in summer (from June 1 to Sept. 15) to avoid these emissions. Individual states may have their own emissions and RVP regulations on top of that.
Not only is summer gasoline the more appropriate kind to use in your lawnmower in the summer, it’s also more fuel-efficient—so you’ll be able to mow more grass with the same amount of fuel.
Gasoline only lasts a few months unless you treat it
There’s another issue with keeping a can of gasoline around from season to season: the stuff expires!
Gasoline is usually understood to last about three to six months from the date you pumped it. Storage conditions will affect that: In the summer heat, it won’t last as long. The type of gasoline also affects how long it lasts. Summer gasoline is often a gas/ethanol blend, and those only last one to three months.
If you know you won’t use up the can of gas anytime soon, you can treat it with a fuel stabilizer like Sta-bil to keep it good for about two years. This won’t rejuvenate gas that has already been sitting around a while, but you can add it to a fresh can of gas to be sure it will still work next season.
What about that old can of gas that you’re just realizing is useless now? You can take it to a hazardous waste disposal center, or look for a hazardous waste disposal event in your area. We have more here on how to dispose of old gasoline.
